snd_pcm_hw_c...raint_mask64(9)

📦 version 7.3.1, in nixpkgs unstable

💅 snd_pcm_hw_c...raint_mask64(9) — bestie edition 🎀

okay so real talk, this is a page straight out of the Kernel API Manual, section 9, and it's literally the snd_pcm_hw_c...raint_mask64 man page. yes the title is truncated with ... — that's not me being lazy, that's the actual page name, iconic behavior tbh. it's all about ALSA PCM hardware constraints and slapping a bitmap mask onto a parameter. let's get into it ✨

🌸 NAME 🌸

snd_pcm_hw_constraint_mask64 — apply the given bitmap mask constraint 💫

like, that's the whole job. one (1) job. and it does it.

🦋 SYNOPSIS 🦋

int snd_pcm_hw_constraint_mask64 (struct snd_pcm_runtime *runtime ,
snd_pcm_hw_param_t var , u_int64_t mask );

three args, returns an int, no cap. 🫶

🎀 ARGUMENTS 🎀

  • runtime — the PCM runtime instance, aka the whole situation you're working with. it's a struct snd_pcm_runtime *, so yes, a pointer, handle it responsibly bestie 💅
  • var — the hw_params variable you're applying the mask to, typed as snd_pcm_hw_param_t. this is the "which thing are we constraining" slot ✨
  • mask — the 64bit bitmap mask itself, a u_int64_t. sixty-four bits of pure intent 🧚

✨ DESCRIPTION ✨

Apply the constraint of the given bitmap mask to a 64-bit mask parameter.

that's it, that's the description, and honestly? it ate. you hand it a 64-bit bitmap mask, you hand it a parameter, and the mask constraint gets applied to that parameter. no drama, no side quests. lowkey the most straightforward little function in pcm_lib.c 🔥

💀 RETURN 💀

Zero if successful, or a negative error code on failure.

so: 0 = slay, negative number = not slay. classic kernel convention, fr fr. always check your return value, don't be that person 🙈

🌈 SEE ALSO 🌈

Kernel file ./sound/core/pcm_lib.c — yes, that's where the magic lives 👑

and then the whole friend group, in order, no skips:

that's thirty of them, go read them all, i'll wait 💖

quick vibe check: the only thing this function promises is zero on success or a negative error code on failure. that's the entire contract, don't go reading anything else into it 🫧

and that's the page!! 🎉 sign-off time: this one came out of ./sound/core, dated October 2026, in the Kernel API Manual — so if you're citing it in your kernel patch changelog, that's your source and your date, bestie. periodt. 👑💜

📦 where this page comes from